Neuronal signal transduction is carried out by such a manner that a neurotransmitter such as serotonin and norepinephrine is released from the terminal of presynaptic neuron and binds to various receptors on the postsynaptic neuronal plasma membrane (synaptic transmission). For the next synaptic transmission, the neurotransmitter existing in the synaptic cleft is subjected to reuptake via an uptake site existing in the presynaptic nerve terminal.
When the reuptake is inhibited, concentration of the neurotransmitter in the synaptic cleft becomes high whereby stronger signal transduction takes place.
At present, many compounds having a serotonin reuptake inhibiting activity and a norepinephrine reuptake inhibiting activity have been known. Those known compounds inhibit the reuptake of serotonin and norepinephrine in presynaptic cell membranes whereby various pharmacological effects are exerted and they are used as therapeutic agents for various diseases throughout the world (refer, for example, to NPL 1).
Examples of specific indications by serotonin and norepinephrine reuptake inhibitors include depression, panic disorder, anxiety, obsessive-compulsive disorder, chronic pain, fibromyalgia, obesity, stress urinary incontinence, and overactive bladder (NPL 2 to NPL 10).    [NPL 1] Kent J M, Lancet, 355, 911-918, 2000    [NPL 2] Tremblay P and Blier P, Curr Drug Targets, 7(2), 149-158, 2006    [NPL 3] Cloos J M, Curr Opin Psychiatry, 18(1), 45-50, 2005    [NPL 4] Dhillon S et al., CNS Drugs, 20(9), 763-790, 2006    [NPL 5] Kamijima K and Aoki M, Expert Rev Neurother, 6(7), 945-956, 2006    [NPL 6] Grothe D R et al., Pharmacotherapy, 24(5), 621-629, 2004    [NPL 7] Rooks D S, Curr Opin Rheumatol, 19(2), 111-117, 2007    [NPL 8] Hainer V et al., Ann N Y Acad. Sci., 1083, 252-269, 2006    [NPL 9] Mariappan P et al., Eur Urol., 51(1), 67-74, 2007    [NPL 10] Andersson K E, Urology, 55(5A Suppl), 51-57, 2000